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UV/IR - what do they mean?

  1. Jul 17, 2009 #1
    UV/IR - what do they mean??

    Alright, I'm posting here in sheer frustration. I've read a bunch of papers lately which mention the ultraviolet and infrared in pretty strange ways - talking about a theory's UV-completeness or if it's UV-finite, IR modification, and so on.

    So - what does this mean? I've scoured the web and papers looking for a definition but I have yet to find a single paper bothering to define the terminology. Thanks!
  2. jcsd
  3. Jul 17, 2009 #2


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    Re: UV/IR - what do they mean??

    These refer to concepts of the renormalization group in quantum field theory, and can't be explained adequately in a brief reply. A theory is said to be "UV complete" if the ultraviolet cutoff can be consistently taken to infinity. For example QCD is UV complete, but QED is not.
  4. Jul 17, 2009 #3
    Re: UV/IR - what do they mean??

    No, I wouldn't expect that to be explainable in a brief reply, but thanks :) I suppose I'll wait for a QFT class then.
  5. Jul 18, 2009 #4
    Re: UV/IR - what do they mean??

    Ramparts -> QFT, as you might already know, is literally plagued with infinities. That's why you frequently hear people talking about "renormalization" of a theory - "removing" those infinities. The two most frequently encountered ones are ultraviolet divergencies (so called as they are associated with large values of momenta, i.e. short wavelengths - hence "ultraviolet") and infrared divergences (theories with massless particles have problems also with small momenta/large wavelengths - hence "infrared"). And those terms you came across refer to ways to handle/modify a theory, if possible, so as to "solve" the problem of divergences in a physically and mathematically meaningful way.
  6. Jul 18, 2009 #5
    Re: UV/IR - what do they mean??

    Thanks, DrFaustus :) I've done some wiki-ing (now that I know where to even look) and I've got a better idea, but obviously I'll have to wait to really learn some QFT to get an understanding. Oh well, I was just wondering what these papers were saying.
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